“The president believes that continued U.S. leadership can be most productive through his participation at the end of the Copenhagen conference on December 18th rather than on December 9th,” said a statement from Robert Gibbs, the White House press secretary. “There are still outstanding issues that must be negotiated for an agreement to be reached, but this decision reflects the president’s commitment to doing all that he can to pursue a positive outcome.”

Mr. Obama was initially planning to visit Copenhagen on Dec. 9 as he makes his way to Oslo, Norway, where he is scheduled to accept the Nobel Peace Prize on Dec. 10.

The change in the schedule brings new life to the concept of shuttle diplomacy, with the president making two trips to Europe in as many weeks.

The White House said that it was working out details of his schedule, but the back-to-back visits raise the possibility that Mr. Obama could either drop by Afghanistan or find time to complete another piece of outstanding business: signing a new arms treaty with Russia.

The old cold-war-era pact, the Strategic Arms Reduction Treaty of 1991, known as Start, expires Saturday. Both sides are close to reaching a deal. By Dec. 18, perhaps the agreement will be reached, and Mr. Obama and Russian President Dmitri A. Medvedev will meet to affix their signatures to it.

President Obama drew criticism on Thursday when he said, “we don’t have a strategy yet,” for military action against ISIS in Syria. Lawmakers will weigh in on Mr. Obama’s comments on the Sunday shows.Read more…